This research proposal is for an investigation into the mechanisms by which bacteria acquire the enzymatic abilities to permit them to utilize novel and uncommon chemicals as growth substrates. Specifically studied will be the ability of organisms in the genera Klebsiella and Escherichia to develop efficient metabolic pathways to permit them to survive and multiply when presented with certain uncommon carbohydrates as sources of carbon and energy. Special attention will be given to the carbohydrate D-arabinose. Mutations predicted to improve or otherwise influence the metabolism of D-arabinose in mutants which have gained the ability to utilize this sugar will be selected in wildtype Klebsiella and transduced into the D-arabinose-positive strain. The influence of such mutations on the growth rate of the organism on D-arabinose can then be documented. Since a ribitol catabolic pathway has now been introduced into Escherichia coli K-12 by genetic techniques, it is now possible to conduct similar experiments using the latter organism.